Apparatus for the production of aryl phosphates



Oct. 18, 1938.

FiA L, SHUMAN APARATUS FOR` THE PRODUCTION OF ARYL PHOSPHATES OriginalFiled Nov. 20, 1935 1N VENTOR. S//l/M/V ATTORNEYS Patented Oct. 18, 1938UNITED STATES APPARATUS FOR THE PRODUCTION OF ARYL PHO SPHATES Royal L.Shuman, Newark, N. J., assignor to Celluloid Corporation,

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a corporation of New Jer- Original application November 20, 1935, SerialNo. 50,714. Divided and this application June 18, 1936, Serial No.85,952

2 Claims.

This invention relates to the preparation of aryl phosphates and moreparticularly to the preparation of tricresyl phosphate by the treatmentof cyclohydroxylic compounds with phosphorus pentachloride.

This invention is a division of the invention disclosed in myapplication S. No. 50,714 filed November 20, 1935.

Heretofore aryl phosphates have been prepared by treating aryl acidswith a phosphorus compound, particularly phosphorus oxychloride, atrelatively high temperatures, namely about 300 C. and for long periodsof time. Other processes involving phosphorus halides have necessitatedthe use of two reaction chambers. In all processes heretofore employedhave required that the ingredients entering into the basic reaction beabsolutely dry.

It is an object of the invention to prepare aryl phosphates by a processusing phosphorus pentachloride wherein the reactions necessary to formthe phosphates are carried out simultaneously and in one reactionchamber. Another object of the invention is the production of arylphosphates using phosphorus pentachloride wherein the aryl acids, i. e.cyclohydroxylic compounds, and other reagents and ingredients need notbe introduced into the reaction in an absolutely dry condition. Anotherobject of the invention is to prepare aryl phosphates at or near roomtemperature, thus producing light colored aryl phosphates as thereaction at the lower temperatures avoid charring, decomposition,degradation or tarry substances associated with the making of arylphosphates at high temperatures. Other objects of the invention willappear from the following detailed description.

Any suitable device may be employed for carrying out my invention.However, a preferred device for carrying out my invention, which deviceforms a part of my invention, is shown in the accompanying drawing. Inthe drawing, wherein like reference numerals refer to the same orsimilar elements,

Fig. 1 is a side View, partly in section, of an apparatusfor use informing aryl phosphates, and

Fig. 2 is an end View, partly in section, of the apparatus shown in Fig.1.

Among the advantages of this invention is that aryl phosphates may beprepared without the aid of applied heat, with a much shorter reactionperiod, higher yields, use of chemicals that are not absolutely dry andin a single step and apparatus. 'Ihe production of aryl phosphates, bythe process of this invention, is economical and adapted to large scaleproduction and is simple compared with prior methods wherein prolongedheating up to and above 300 C. is employed. The aryl phosphates may bemoisture, preferably in the form of a Vapor, such 1 as moist air, tocomplete the reaction. Hydrogen sulphide may be substituted for moistureto produce the thiophosphates. The chemical reactions taking place areprobably as follows:

(1) 3 (CHsCsHqiOH) +PCl5+H2O= (CHaCeHiO) 3PO -l- 5HC1 (2) 3 (CSI-15CH)+PC15+H2S= (CGI-150) SPS -i-5HC1 In the foregoing, cresol and phenol aresimply used to illustrate the probable reactions which take place.However, any of the hydroxy derivatives of the benzene series, forinstance, the phenols, may be employed. Classified under the name ofphenols, including phenol itself, are the isomeric cresols and xylenolsand their higher homologues. Under the generic term phenols it isintended to include not only the monohydric but also the polyhydricphenols, such as resorcinol, and also the naphthols. More generallystated, any of the hydroxy derivatives of carbocyclic hydrocarbonswherein the hydroxy radicle is attached to the nucleus may be employed.Also, mixtures of two or more of these compounds, or mixtures of all ofthem, such as is found in tar acids commercially sold under the name ofcresylic acid, may be used. The products resulting from this reactionmay be homogeneous phosphoric esters of hydroxy derivatives of thebenzene series, such as phenol, cresol, etc., or they may be mixedesters of phosphoric acid, depending upon the materials used. Theseesters are generally known and described as aryl phosphates.

In addition to the aryl phosphates described above, phosphates from thenaphthols (alpha and beta naphthols) and ring alcohols of thehydro-aromatic carbons, such as cyclohexanol and methyl cyclohexanol maybe made by this process.

The structure of homogeneous phosphoric acid esters may be representedas follows:

/O R1 OP--Rl or R2 Where RI, R2 and R3 represent different radi- Cles ofaromatic compounds, for instance, RI may represent phenyl, R2 mayrepresent cresyl, while R3 may represent naphthyl. Y Y

In the foregoing graphic formulas an SP group may be substituted for theOP group. Whether a phosphate or a thin-phosphate is produced willdepend upon whether water or hydrogen sulphide is added to the reaction,as more fully illustrated by the empirical formulas (1) and (2) setforth above.

The properties of the estersproduced may be described as crystallinesolids or oily liquids, light in color, odorless, neutral, inert, verystable and non-flammable. They may be distilled under reduced pressurewithout decomposition and they have a boiling point of approximately 300C. at a reduced pressure of 10-15 mm. mercury. The specic gravity of theesters may vary from 1.15 to 1.22.

The aryl phosphates formed in accordance with this invention are ofgreat importance as plasticizers in plastic compounds and coatingmaterials. When such aryl phosphates are incorporated in plasticcompositions and coating materials which contain derivativesofcellulose, such as nitrocellulose or pyroxylin, cellulose acetate andcellulose ethers, for instance, benzyl cellulose, and which may containresins, due to their low vapor pressure, they remain a part of the solidconstituents in forming lms even at elevated temperatures, thus'keepingthe lms plastic and flexible and making them more durable. The arylphosphates are also solvents or partial solvents for cellulose estersand resins and, therefore, materially aid in their absorption to producehomogeneous products.

'I'he aryl phosphates produced in accordance with this invention mayalso be used extensively as absorbing agents in recovery systems forsolvents and for phenols in gas liquors. The aryl phosphates also nd animportant use in air purifying apparatus for absorbing abnoxious vaporsand entrapping dust or other solid particles.

The aryl phosphates produced in accordance with this invention may alsobe employed as plasticizers in wax coatings, as re and waterproofingagents, as vehicles for grinding pigments, as the sole constituent or asa diluent in transformer oil, as lubricants with or without othermodifying agents, as joint compounds for electrical cables, as softenersand modifiers for rubber, chlorinated rubber and resins, in soaps, inpolishes, in inks, as rust-proofing agents, vin leather finishes, in furdressing, in insecticides and moth-proofing agents and in caulkingcompounds. The aryl phosphates produced in accordance with thisinvention, and especially tricresyl phosphate, may be employed as thelubricant in gas compressing devices whether saidk device be of thepiston type'or the centrifugal type. They are of particular importancein devices for compressing oxygen for medical and industrial purposes.Oxygen, when being compressed in the presence of a hydrocarbon as thelubricant for the compressor, forms explosive mixtures under thetemperatures and pressures employed whereas tricresyl phosphate is notonlyequally as good a lubricant for the device but is also inert withrespect to the oxygen; not effecting it in any way.

As an aid in describing the invention, the apparatus shown in thedrawing will now be described. The apparatus may comprise a kettle,

or reaction chamber, I having a jacket 2 surrounding the same. Thekettle may be of any convenient size and formed of any suitable metallined with enamel, or it may be formed of any other corrosion resistingmaterial. The kettle may be equipped with a reiux condenser 3. A conduit4 leading from the kettle to the reflux condenser is provided for thepurpose of carrying vapors into said reux condenser, while a conduit 5is provided for returning to the reaction kettle any condensate formedin the reilux condenser. A conduit 6 is provided for carrying any gasemitted from the reflux condenser to scrubber 'I adapted to absorb anyhydrochloric acid coming from the reilux condenser. The scrubber l isprovided with a conduit 8 for supplying it with an absorbing materialand a conduit 9 for carrying the absorbent and absorbed hydrochloricacid to a suitable reclaiming system.

The reaction kettle is provided with an opening I I which opening isconnected by a conduit I2 to a rotary or other suitable charging andmeasuring device I3. The charging and measuring device I3 is connectedvby a conduit I4 to a hopper I5 having a funnel-shaped bottom I6. Theupper part of the hopper I5, which is preferably suiiiciently large tocontain a drum I? of phosphorus 'pentachloride is provided with a doorI8 adapted to form an opening of suiicient size to permit of the rollingof a drum into and out of the hopper. If desired, the door I8 may beplaced at the top of hopper and the drum I 'I charged and dischargedvertically into the hopper. When the door I8 is in closed position thehopper is substantially 'air tight. Mounted in the upper part of thehopper and adapted to support the drum I 'I are shafts I9, two innumber. The shafts I9 are equipped with rollers 2I of such constructionthat they engage the drum and rotate the same and also prevent the drumfrom axial movement. The shafts I9 may be propelled by suitablemechanism 22 driven from any suitable source of power supply as anelectric motor 23. The charging and measuring device I3 may also bedriven from the same electric motor by means of a chain or belt 24.

Mounted in a suitable bearing 25, which is attached to the upper part ofthe hopper I5, is a device 2E so constructed that it may be attached tothe head of the drum I1 for moving the head g of the drum toward andaway from said drum, or in other words, for opening and closing thedrum. The hopper I 5 may also be provided with an inlet 2'! and anoutlet 28. The'inlet y2'! is connected by a conduit 29 to a gas dryingdevice 3l, which in turn is connected by a conduit 32 to a source of airor other inert gas. The arrangement is such'that dry air or other inertgas may be injected into the upper part of the hopper and withdrawnthrough the outlet 2l. The air cr gas is adapted to remove any ventedgases from the hopper, the air or gas being dry merely for the purposeof preventing bridging or caking by the phosphorus pentachloride. Thedrying device 3I may dry the air or gas by any suitable'method, such asby passing the same in contact with calcium chloride, sulphuric acid orother air drying compounds. A port or door 30 may be provided in thedrying device 3I for charging it with the drying medium and for cleaningpurposes. 'I'he outlet 28 is connected by a conduit 33 to the conduit 6,thus passing any gas drawn through the upper part of the hopper I5 intothe scrubber 'I for the purpose of reclaiming any hydrochloric acid inthe vented gases.

The reaction kettle I is provided with an opening 34 connected by asuitable conduit 35 to a supply tank 36 adapted to hold a measuredquantity of hydroxy derivatives of an aryl compound, for instance,cresylic acid. The reaction kettle is provided with another opening 31connected by a suitable conduit 38 to a gas moistening apparatus 39.This moistening apparatus may comprise a chamber 4I having therein asteam coil 42 connected to steam inlet 43 and outlet 44. A suitableconduit 45 is provided for injecting into the chamber 4l a suitablequantity of water. A drain and cleanout opening 46 may be provided atthe bottom of the chamber 4|. Above the steam. coil 42 may be positioneda wire screen or perforated plate 41 for supporting a layer of materialsuch as felt, cotton duck, etc., which layer is kept wet by thecondensed vapor, which vapor is formed by the steam coils heating thewater in chamber 4l. Above the screen or perforated plate 41 is an inlet48 through which air under pressure is adapted to be injected into themoistening device.

The hopper l is so constructed that the drum or other container ofphosphorus pentachloride may be placed in a substantially horizontalposition on rollers. When the door is closed the hopper is substantiallygas tight. By means of device 26 the drum head may be removed from thedrum and moved any desired distance therefrom from the-outside of thehopper without exposing the phosphorus pentachloride to the air. Thedrum may revolve on the rollers 2l, or, if desired, it may be vibrated,so that the m'aterial in the drum. may be removed therefrom at a slowrate. The rate of turning of the drum and the width of the openingbetween the drum and drum head are adapted to regulate the flow ofphosphorus pentachloride into the hopper. It is desirable not to ll upthe hopper as it may cause clogging and bridging of the phosphoruspentachloride, thereby interrupting the free feeding of same.

The air humidifier 39 is so constructed that warm saturated moist airmay be fed into the reaction kettle. The moist air is preferablymaintained, at the point of entrance into the reaction chamber, at atemperature of from 50-60" C. and contains approximately .006 pound ofwater vapor per cubic foot. Although this amount of water vapor percubic foot is preferable, the air may contain from .01 down to as littleas .0005 pound of water per cubic foot. In place of moist air, any otherinert gas containing the required amount of moisture may be employed.Moist steam may also be used. As the gas entering through line 38 isemployed to convey moisture into the reaction chamber and also agitatethe contents of the kettle the use of air is preferable as it isaccessible and allows for an ease of control of the moisture enteringthe reaction. However, a product having a clearer color results whenmoist carbon dioxide or other non-oxidizing gas is employed instead ofair. The conduit 38 may extend to the bottom of the reaction kettle andthe air or other gas passing through the contents of the kettle willthoroughly agitate the same.

The bottom of the reaction kettle is equipped with an opening 5I) andconduits 5| and 52. Conduit 5l leads to a drain while conduit 52connects the reaction kettle with a storage tank 53 for receiving andretaining the products of the reaction. A conduit 54 is provided toconnect the supply tank with the purifying apparatus, etc.

The jacket 2 of the reaction kettle is supplied with a steam inlet 55and water outlet 5G and an inlet 51. By means of suitable valves in thelines 55, 56 and 51 steam or water may be circulated in the jacket toregulate the temperature of the reaction kettle.

As an illustration of the process and the way it is carried out whenemploying the apparatus shown in the drawing, the following sizes andproportions are given. For the purpose of illustration, the equipmentmay consist of a 200 gallon enameled, jacketed reaction kettle having aIhopper large enough to hold a 55 gallon open head drum which contains550-600 pounds of phosphorus pentachloride. A charge for the equipmentdescribed consists of 860 pounds of cresylic acid and 550 pounds ofphosphorus pentachloride. The cresylic acid may be of the commercialgrade and contain up to 1% or more 'of dissolved water and up to 5% ofwater in suspension. By this invention a drying of the cresylic acid ismade unnecessary. The cresylic acid is first charged into the reactionkettle and the phosphorus pentachloride is then added at the rate ofapproximately 5 pounds per minute. Warm air containing the proper amountof moisture is blown into the reaction kettle at the same time so thatit enters the bottom of the retort. If the cresylic acid contains anexcessive amount of water, correction may be made to the amount of watervapor introduced. This injection of air actively agitates the solutionin the kettle and removes quickly the hydrochloric acid gas as it isformed. After commencement of the action, the rate of the flow of theair preferably is regulated so that slightly less moisture is presentthan required to cause the secondary reaction to take place as follows:

When the phosphorus pentachloride has all been added, the iow of warmsaturated air is continued until the reaction is complete. This may bedetermined by taking a sample from the reaction chamber and adding waterslowly. Although it is preferred to have a slight deficiency of moisturepresent during the addition of the phosphorus pentachloride, this is notnecessary and good yields may be obtained when there is present at alltimes sufficient water to cause the secondary reaction. When there is noevolution of hydrochloric acid gas with the addition of water thereaction is regarded as complete.

This process and apparatus is of substantial importance for the chemicalmanufacture of the aryl phosphates. In this process it is not necessaryto use heat as the heat of reaction is sufficient to raise thetemperature beyond the temperature desired or required so that coolingis often necessary to keep the temperature down. The temperature shouldnot exceed 125 C. and it is preferable to keep the temperature atapproximately 80 C. However, higher temperatures may be used without anysubstantial disadvantage. It is preferable that when the temperatureexceeds 75 C. the feeding of phosphorus pentachloride be interrupted fora short time. The time cycle for making aryl phosphates by this processdoes not exceed 6 hours and it may be considerably shortened.

'I'he tricresyl phosphate obtained by this process is light in color andcontains some hydrochloride and phosphoric acids, free phenols and otherimpurities so that further refining may be required when the productsare to be used for Certain purposes. The yield of aryl phosphates byemploying this invention may be as high as SiS-99.5% of the possibletheoretical yield. When employing the aryl phosphates as lubricants andfor like purposes a further refining is unnecessary as the small amountof free phenols and acids that it contains are not injurious and oftenactually assist in forming such lubricating compounds or in the use ofthe compounds. However, when the aryl phosphates are to be used inconnection with medicines, wrappings for food, for the manufacture oftransparent plastic articles and other uses, it may be necessary to renethe same. Any method of rening aryl phosphates may be employed. Forinstance, the usual refining treatment may be given the aryl phosphates,when refining treatment consists in distilling the crude product under ahigh vacuum and washing the distillate with a hot dilute (2%) causticsolution and then with hot water to remove traces of alkali, The thuspuried aryl phosphates may then be given an alkali permanganatetreatment, a Zinc and acid treatment or other treatments to furtherremove any impurities.

Although any method of reiining the aryl phosphates maybe employed, Iprefer to use the following method in which usual distillation inreiining aryl phosphates may be eliminated resulting in a saving of rawmaterials, thus making for a more simple and economical process. Acharge of the crude aryl phosphate is put in a suitable jacketed enamelVlined kettle equipped with agitators. To this charge an equal volume ofhot water is added and the temperature raised to 90-95" C. Sufficientsodium sulphide or other alkali or alkali with sulphide is then added tomake a 3 to 5% solution based on the water present. The material in thekettle is then agitated for 10 to 30 minutes and then allowed to standuntil the aryl phosphate settles to the bottom and the aqueous solutiongoes to the top forming separate layers. The supernatant liquid is drawnoli and an additional charge of hot water equal in volumeY to the firstcharge is added. The solution is then heated to 90-95o C. while beingagitated and sufcient caustic alkali and sodium sulphide or other alkalisulphide are added so that the hot water will contain approximately 11/2to 31/2% of sodium sulphide and l to 3% of caustic alkali. The contentsof the Ykettle are again decanted and the aryl phosphate is Washed withhot water. The aryl phosphate may then be passed through a filter toremove the sulphides which have been formed due to the treatment withsodium sulphide. To remove some impurities and color, the foregoingtreatment may be modied by first treating a crude aryl phosphate with lto 3% of zinc powder. and a small amount of mineral acid at atemperature near the boiling point of water. It is preferred to use thistreatment as the Iinal step.

Treatment with zinc and mineral acid may be as follows: The lteredpartially purified aryl phosphate is washed 3 or 4 times with a dilutealkali solution so that any phenols and intermediate or unstableproducts remaining after the preliminary treatment may be removed. Mostof the alkali is then removed by washing with hot water. There is addedto the charge, in a volume equal to the aryl phosphate present, waterheated to 90 C. and approximately 1% of Zinc powder is stirred into thesolution. Sufficient hydrochloric or sulphuric acid is then added ,tocombine with the zinc and release nascent hydrogen. The charge isagitated during the release of the nascent hydrogen and continued forfrom l0 to 30 minutes and the temperature of the charge maintained atabout 95 C. After the aryl phosphate separates from the water solutionupon standing, it is passed through a centrifuge at a temperature above90 C. to completely dehydrate it and remove other impurities andsuspended matter. The above treatment will be found suiiicient forproducing a product of purity required for most uses, However, iffurther reiining is desired to remove the last traces of impurities, thearyl phosphate may be treated with a water-soluble permanganate. TheZinc treatment described in the foregoing may be given after thepermanganatetreatment and this is sometimes found desirable. Otherdiscoloring agents, such as activated charcoal, fullers earth, aluminumor like products, may be employed for filtering impurities from thecrude phosphate eliminating one or all of the purifying steps describedabove.

The alkali solution used in treating aryl phosphates may be formed ofthe hydroxdes of any of the alkali metals or alkali earth metals ormixtures of the same. Hydrogen or sodium peroxide may be used inconnection with the alkali washes to remove oxidizable impurities.Monosodium (sodium peroxide) oxide may also be used for this purpose.

In place of using the zinc and acid treatment, an electric current maybe passed through a charge maintained in hot water, between zincelectrodes, or one zinc electrode and an electrode of another materialsuch as carbon.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis:

1. In an apparatus for producing aryl phosphates, the combination with areaction chamber, of a substantially air-tight hopper connected to saidreaction chamber, means in said hopper for supporting a drum containinga reaactant, said drum supporting means being adapted to rotate saiddrum to slowly discharge the reactant from said drum, means attached tosaid hopper and adapted to be operated externally thereof for openingand closing said drum and means between said drum and said reactionchamber for feeding a predetermined quantity of the reactant to saidreaction chamber.

2. In an apparatus for producingl aryl phosphates, the combination witha reaction chamber, of a substantially air-tight hopper connected tosaid reaction chamber, means in said hopper for supporting a drumcontaining a reactant, said drum supporting means being adapted torotate said drum to slowly discharge the reactant from said drum, meansattached to said hopper and adapted to be operated externally thereoffor opening and closing said drum, means between said drum and saidreaction chamber for feeding a predetermined quantity of the reactant tosaid reaction chamber and an air humidifier connected with said reactionchamber.

ROYAL L. SHUMAN.

